Prediction and Control of Turbulence Based on Turbulent Elementary Vortices

为了了解湍流中的基本涡，并将其应用于工程问题，采用直接数值模拟的方法研究了各种湍流中基本涡的特性。结果表明，基本旋涡的特性与一种湍流类型和雷诺数无关，它们在高雷诺数湍流中形成大尺度的团簇。平面槽道流动的大尺度数值模拟表明，近壁区的涡流是普遍存在的，而远壁区则表现为条纹状结构。此外，这种结构并不持续，但在数值试验中出现了滚子涡旋，计算区域的跨向宽度受到了严格限制。阐明了基本旋涡的标量输运机理和湍流中标量表面的分形特征。利用直接数值模拟技术对壁面湍流的主动反馈控制进行了研究。关于雷诺…的调查对于实际应用中出现的高雷诺数流动，控制效果对LDS数的依赖性更强，也说明了所提出的控制方法的有效性。结果表明，现有的控制算法对于湍流管流也是有效的，并且我们证明了仅基于壁面上可测量的信息来减阻的可能性。研制了阵列式传感器和变形膜式磁致动器组成的反馈控制系统样机，并对其性能进行了评价。采用数值模拟的方法，研究了添加剂、壁面操纵和压力梯度对湍流流场的影响。分析了颗粒流中颗粒分布不均匀、颗粒旋转、布料效应、加减速空间发展场等因素对流场的影响。为了建立新的SGS模型，利用高雷诺数湍流的数值模拟方法研究了湍流的层次结构和不同尺度之间的能量传递机制。较少

To understand elementary vortex in turbulence and to apply it for engineering problems, characteristics of the elementary vortex in various turbulent flows are investigated by direct numerical simulations. It is shown that the characteristics of the elementary vortex are independent of a type of turbulent flows and Reynolds number, and that they create large-scale clusters in high Reynolds number turbulence. Large scale DNS of plane-channel flow reveals that vortices in near-wall region are universal and that the far-wall field is characterized by streaky structures. In addition, such a structure was not sustained but roll-cell vortices appeared in the numerical experiment, in which spanwise width of computational domain was strictly restricted. Scalar transport mechanism by the elementary vortex and fractal characteristics of scalar surface in turbulence are also clarified. R&D studies on active feedback control of wall turbulence are performed by using DNS. Investigation on the Reyno … More lds number dependency of the control effect reveals the effectiveness of the proposed control for high Reynolds number flows appearing in real applications, too. It is shown that the existing control algorithms are also valid for a turbulent pipe flow, and we demonstrate the possibility of drag reduction based on the information measurable on the walls only. A prototype feedback control system with arrayed sensor and deformable-membrane-type magnetic actuators placed in a matrix is also developed and evaluated. Turbulent flow fields modulated by additives, manipulation at the wall or pressure gradient were investigated by means of DNS. Namely, influences of the non-uniformity of particle distribution and particle rotation in particle-laden flows, effect of fabric planting, and spatially developing field with acceleration or deceleration were analyzed. To develop new SGS model, hierarchical structure of turbulence and energy transfer mechanism between different scales are investigated using DNS of high Reynolds number turbulence. Less